David Capocci woke up at the guest house he runs near Mount Pilchuck just before 3 a.m. on Friday. His two dogs, Titus and Kobe, were barking like crazy, so his husband groggily got up to let them out.
Outside, their 15 alpacas were calm as could be.
“Meanwhile, I’m bouncing out of bed going, ‘That was an earthquake, that was an earthquake,’ ” Capocci said. “The herd of alpacas didn’t even blink an eye.”
A magnitude 4.6 earthquake shook Seattle and the Puget Sound region at 2:51 a.m. Friday, according to the United States Geological Survey (USGS), rattling some people (and dogs) out of bed, while leaving other people (and alpacas) blissfully dormant and unfazed.
The earthquake emanated from Three Lakes, Snohomish County, about 9 miles east of downtown Everett. The temblor raises the probability of a larger earthquake in the next few days, although the likelihood of a bigger quake is still very small, the USGS said. There is a 4% chance of a quake larger than Friday morning’s within the next week, according to the USGS.
“There’s an elevated possibility of a larger earthquake in the next few days, but it is very small and it shrinks quickly in time, too,” said Paul Bodin, a University of Washington seismologist and manager of the Pacific Northwest Seismic Network. “So if there’s nothing within a week, then the probability of it being in the next week is vanishingly small.”
At most, the earthquake, nearly 18 miles below the earth’s surface, lasted a “couple seconds,” said Joan Gomberg, a USGS seismologist and affiliate faculty member at UW, though shaking can feel longer “because some houses reverberate a little bit.”
The Snohomish County Sheriff’s Office said it had not received any reports of damage. Police in nearby Lake Stevens reported no damage to city infrastructure. And the Washington State Department of Transportation said it inspected bridges and infrastructure following the quake and found no damage.
Bodin said that the seismic station closest to the earthquake registered shaking that “could possibly, just barely, have caused damage.”
Calls to regional 911 centers did spike — including by nearly 700% in Snohomish County — something emergency officials frown upon, hoping to keep lines clear for those who need them.
A second quake, measured at magnitude 3.5, was reported near Monroe a few minutes later. A handful of smaller aftershocks followed, according to the Pacific Northwest Seismic Network.
Initial USGS reports had described the larger trembling as a magnitude 4.4 earthquake that began less deep in the earth’s surface.
The earthquake was the product of a thrust fault, in which one side of a fault pushes upward in relation to its opposite side, according to Paul Caruso, a USGS geophysicist. Thrust faults are common in the Cascade Range, Caruso said.
He said the earthquake did not have any connection to recent tremors in California, and that it was too shallow to have originated in the Cascadia subduction zone off the Washington coast, where “stress and strain has been building for a long time.”
The biggest fault near the earthquake is the Southern Whidbey Fault Line, but Gomberg said researchers don’t suspect this event occurred on that fault.
The earthquake happened at “a complex nexus of faults” and, because it happened so deep, it’s unlikely that researchers will determine with certainty which fault was the origin, Bodin said.
“We really don’t know what they do at that depth,” he said. “This earthquake was deep enough, it could be on any of them.”
The larger earthquake was felt across the Canadian border, the USGS map reports. People reported feeling the earthquake to the south in Olympia, to the west in Port Angeles and to the east in Wenatchee.
Kieran Smith, 23, a Western Washington University student in Bellingham who lives in a fourth-floor apartment, said he felt his bed shake and the building sway.
On social media, many reported waking up or sensing the earthquake.
In Arlington, Tristan Halsen, 20, an Everett Community College student, was sitting on his couch working on homework when he heard a “really loud rumbling like a stampede,” he said in a Twitter message. A wall-mounted TV began shaking. At first, he thought it was a thunderstorm. Then, his house began shaking “for what seemed like forever,” he said.
“I think this was my first ‘big’ earthquake that I can remember and it was interesting to experience one this big,” he wrote.
Leah Kennebeck, who lives in Seattle’s Queen Anne neighborhood, said in a Twitter message that she woke up from a dream to her bed shaking and her ceiling light fixture rattling.
She “sat straight up and froze” trying to feel if the shaking was getting worse, she said.
“Once I realized things were rattling in my room longer than if it was from something like a truck going by, I knew it was an earthquake,” she said.
Kennebeck, who last felt shaking during the magnitude 6.8 Nisqually earthquake in 2001 in grade school, said the quake left her with an unsettling feeling, particularly after a string of powerful earthquakes in California last week.
“Scared the crap out of me,” she wrote. “My 4th grade self would be ashamed.”
She said she’ll be putting together an updated emergency kit later Friday.
This is the third local earthquake of about the same size in the last 10 years. The Kingston Earthquake, in 2009, was a magnitude 4.9 near Poulsbo, and a magnitude 4.7 quake hit near Okanogan in 2011.
The Puget Sound region is one of the most hazardous areas in the country for earthquakes. The Cascadia Subduction Zone lurks offshore and could produce a damaging magnitude 9.0 earthquake, an event expected about every 500 years. But some have come only 200 years apart, and it has been 319 years since the region experienced an earthquake that large. A Seattle Times analysis in 2016 found that about 5.4 million people live in a part of Washington endangered by a magnitude 9.0 earthquake.
Scientists have discovered more than two dozen faults across Washington state that could also produce damaging shaking.
The region is largely unprepared. The state of Washington does not require old, rigid brick and concrete buildings to be retrofitted. Thousands of children attend classes in vulnerable school buildings. The state would need to spend hundreds of millions more dollars to retrofit its bridges. Many county emergency-management departments are staffed with a single employee, The Seattle Times found in 2017.
“It’s the old standard message that we always give,” Bodin said. “We live in a seismically active area and one day the shaking won’t be as it was associated with this earthquake. People should be prepared. Have a plan.”
The Pacific Northwest Seismic Network is developing an early earthquake warning system.
Researchers have been “working furiously” to install new monitoring sites, Gomberg said. A pilot group of businesses, government agencies and schools has early access to the warning system, as its being tested and refined.
Gomberg said the system worked during this earthquake. It provided a few seconds of warning to Seattle that strong shaking was coming. It also assessed, within a few tenths of a magnitude unit, the magnitude of the earthquake, she said.